SAND DOLLARS AS SUSPENSION FEEDERS: A NEW DESCRIPTION OF FEEDING IN DENDRASTER EXCENTRICUS

¹ Department of Biology, University of California, Los Angeles, California 90024

1. Dendraster excentricus used the spines and tube feet to capture large food items such as algal fragments. In addition, the large bidentate pedicellariae were used to capture active prey.

2. Rejection of food occurred at the test surface or at the Y junction of the food grooves. The rejection response was well defined.

3. Specimens of Dendraster from a protected outer coast location ate primarily small crustaceans, diatoms, algal fragments, and sand grains. In a summer sample, diatoms were the most abundant item in the diet; in a winter sample, crustaceans predominated the diet.

4. Sand dollars from a protected outer coast sand dollar bed had more food of higher organic content in their guts than did sand dollars from two bay habitats.

5. Food passed through the stomach in 5 hr and through the entire gut in 2 days. Specimens of Dendraster from a protected outer coast habitat fed continuously.

6. Individuals of Dendraster were nonselective with respect to particle size in the range of 30 µm to 100 µm. Sixty per cent of the particles captured by specimens of Dendraster in the field were < 180 µm in size.

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